feat: implement Interceptor (#3)

Author: tmzane

interceptor.go

@@ -0,0 +1,102 @@
+package queries
+
+import (
+	"context"
+	"database/sql/driver"
+)
+
+var (
+	_ driver.Driver        = Interceptor{}
+	_ driver.DriverContext = Interceptor{}
+)
+
+type Interceptor struct {
+	Driver       driver.Driver
+	ExecContext  func(ctx context.Context, query string, args []driver.NamedValue, execer driver.ExecerContext) (driver.Result, error)
+	QueryContext func(ctx context.Context, query string, args []driver.NamedValue, queryer driver.QueryerContext) (driver.Rows, error)
+}
+
+// DriverName returns the driver name to pass to [sql.Register] and [sql.Open].
+func (i Interceptor) DriverName() string { return "interceptor" }
+
+// Open implements [driver.Driver].
+func (i Interceptor) Open(name string) (driver.Conn, error) {
+	conn, err := i.Driver.Open(name)
+	if err != nil {
+		return nil, err
+	}
+	return wrappedConn{conn, i}, nil
+}
+
+// OpenConnector implements [driver.DriverContext].
+func (i Interceptor) OpenConnector(name string) (driver.Connector, error) {
+	if driver, ok := i.Driver.(driver.DriverContext); ok {
+		connector, err := driver.OpenConnector(name)
+		if err != nil {
+			return nil, err
+		}
+		return wrappedConnector{connector, i}, nil
+	}
+	connector := dsnConnector{name, i.Driver}
+	return wrappedConnector{connector, i}, nil
+}
+
+var (
+	_ driver.Conn           = wrappedConn{}
+	_ driver.ExecerContext  = wrappedConn{}
+	_ driver.QueryerContext = wrappedConn{}
+)
+
+type wrappedConn struct {
+	driver.Conn
+	interceptor Interceptor
+}
+
+// ExecContext implements [driver.ExecerContext].
+func (c wrappedConn) ExecContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Result, error) {
+	execer, ok := c.Conn.(driver.ExecerContext)
+	if !ok {
+		panic("queries: driver does not implement driver.ExecerContext")
+	}
+	if c.interceptor.ExecContext != nil {
+		return c.interceptor.ExecContext(ctx, query, args, execer)
+	}
+	return execer.ExecContext(ctx, query, args)
+}
+
+// QueryContext implements [driver.QueryContext].
+func (c wrappedConn) QueryContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Rows, error) {
+	queryer, ok := c.Conn.(driver.QueryerContext)
+	if !ok {
+		panic("queries: driver does not implement driver.QueryerContext")
+	}
+	if c.interceptor.QueryContext != nil {
+		return c.interceptor.QueryContext(ctx, query, args, queryer)
+	}
+	return queryer.QueryContext(ctx, query, args)
+}
+
+var _ driver.Connector = wrappedConnector{}
+
+type wrappedConnector struct {
+	driver.Connector
+	interceptor Interceptor
+}
+
+// Connect implements [driver.Connector].
+func (c wrappedConnector) Connect(ctx context.Context) (driver.Conn, error) {
+	conn, err := c.Connector.Connect(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return wrappedConn{conn, c.interceptor}, nil
+}
+
+// copied from https://go.dev/src/database/sql/sql.go
+type dsnConnector struct {
+	dsn    string
+	driver driver.Driver
+}
+
+func (t dsnConnector) Connect(_ context.Context) (driver.Conn, error) { return t.driver.Open(t.dsn) }
+func (t dsnConnector) Driver() driver.Driver                          { return t.driver }